1. Factors affecting installation quality
(1) Clamps must not have defects such as pores, sand holes, shrinkage holes, cracks, etc.
(2) The material and performance of the sealing ring must meet the requirements. There must be no bubbles, impurities, cracks, uneven defects on the sealing surface. Aged rubber rings cannot be used.
(3) The theoretical movement distance of the clamp in the clamp is half of the expansion and contraction of the joint. It must be measured. If it cannot be achieved, the expansion and contraction requirements of the pipeline cannot be met. In order to promote the sealing effect, the left and right end pipes are matched with the clamp before leaving the factory. In actual projects, it is not appropriate to use ordinary pipes to directly replace the end pipes. In addition, there are certain requirements for the verticality of the end face of the end pipe and the axis and the flatness of the end face itself. If the size is not standard, the expansion and contraction of the joint will be greatly reduced, which cannot meet the use requirements.
(4) The size of the end pipe diameter must be selected with positive deviation, otherwise the clamp will not have enough pressure on the sealing ring, affecting the sealing effect of the joint.
2. Precautions during installation
(1) The distance between the clamp and the end pipe must be controlled. The distance control should be combined with the instructions. When the gap between the two pipe ends is the smallest, the clamp ring should be exactly against the inclined surface.
(2) When the position of the clamp ring is determined, the size of the gap between the two pipe ends should be determined by calculation based on the elongation of the pipeline and the ambient temperature during construction. The size deviation should be guaranteed during construction.
(3) Under the premise of a certain moving distance, the greater the error in the height and width of the weld between the clamp ring and the end pipe and the verticality of the clamp ring plane and the end pipe axis, the smaller the expansion and contraction of the joint and the worse the use effect.
(4) The splash impurities during the welding of the end pipe and the clamp ring affect the sealing of the end pipe. Before installation, the welding slag on the sealing surface should be removed to ensure the sealing effect.
3. Overview
The groove pipe connection technology, also known as the clamp connection technology, has become the first choice technology for the connection of liquid and gas pipelines. Although this technology was developed later in China than abroad, it was quickly accepted by the domestic market due to its advanced technology. Since the development in 1998, after just a few years of development and application, it has gradually replaced the two traditional pipe connection methods of flange and welding. Not only is the technology more mature, the market is also generally recognized, and it has been actively guided by national laws and policies.
The application of grooved pipe fittings connection technology makes the complex pipe connection process simple, fast and convenient. It has made a big step forward in pipe connection technology.
4. Introduction to grooved pipe fittings
Grooved pipe fittings include two major categories of products: (1) Pipe fittings that play a connecting and sealing role include rigid joints, flexible joints, mechanical tees and grooved flanges;
(2) Pipe fittings that play a connecting transition role include elbows, tees, crosses, reducers, blind plates, etc.
Grooved pipe fittings that play a connecting and sealing role mainly consist of three parts: sealing rubber ring, clamp and locking bolt. The inner rubber sealing ring is placed on the outside of the connected pipe and matches the pre-rolled groove. Then the clamp is buckled on the outside of the rubber ring and then fastened with two bolts. Because its rubber sealing ring and clamp adopt a unique sealable structural design, the grooved connector has good sealing performance, and its sealing performance increases with the increase of fluid pressure in the pipe.
5. Advantages of grooved pipe fittings connection
(1) Simple operation
The connection operation of grooved pipe fittings is very simple and does not require special professional skills. Ordinary workers can operate it after simple training. This is because the product has incorporated a large number of fine technical parts into the finished product in a factory-based manner. It only takes a few minutes to connect a pipe fitting, which greatly simplifies the technical difficulty of on-site operation, saves man-hours, and thus stabilizes the quality of the project and improves work efficiency. This is also the overall direction of the development of installation technology.
The traditional pipe connection method of welding and flange connection not only requires welding workers with corresponding skills, but is also time-consuming, difficult for workers to operate, and there is pollution from welding smoke. Due to differences in operating space and welding skills, it is difficult to achieve satisfactory results in welding quality and appearance, which affects the overall quality of the project.
In addition, since grooved pipe fittings are finished products, the required operating space on site is small, and they can be truly installed against the wall or in the corner, which greatly reduces the difficulty of operation, thereby saving floor space and beautifying the effect of pipeline installation.
(2) The original characteristics of the pipeline are not affected
Grooved pipe fittings only use a groove rolling machine to extrude a groove on the outer surface of the connected pipe without damaging the inner wall structure of the pipe. This is a unique technical advantage of grooved pipe fittings. If traditional welding operations are used, many pipes with anti-corrosion layers on the inner walls will be damaged. Therefore, the specification stipulates that galvanized pipes, plastic-lined steel pipes, steel-plastic composite pipes, etc. shall not be connected by welding and flanges, otherwise secondary processing is required.
(3) It is conducive to construction safety
Using grooved pipe fittings connection technology, only cutting machines, groove rolling machines and wrenches for tightening bolts are needed on site, which is convenient for construction organization. However, when welding and flange connections are used, complex power cables, cutting machines, welding machines, oxygen and acetylene cylinders, etc. are required, which brings complexity to construction organization and also poses the risk of leakage and fire. At the same time, welding slag produced by welding and gas cutting will inevitably fall into the interior of the pipeline, which may easily cause pipeline valves and even equipment to be blocked during use, and also pollute the water quality in the pipe.
In addition, welding and flange connection inevitably require long-term high-intensity high-altitude operations, which are also prone to production safety accidents.
(4) Good system stability and convenient maintenance
The grooved pipe connection method has a unique flexibility feature, which makes the pipeline resistant to vibration, shrinkage and expansion. Compared with welding and flange connection, the stability of the pipeline system is increased and more suitable for temperature changes, thereby protecting the pipeline valves and reducing the damage to the structural parts caused by pipeline stress.
Since the grooved pipe connection operation is simple and the required operating space is reduced, it brings many convenient conditions for future maintenance. When the pipeline needs to be repaired and replaced, only two clamps need to be loosened to replace, rotate, and modify a section of the pipeline at will. There is no need to damage the surrounding walls, which reduces maintenance time and maintenance costs.
(5) Economic analysis
Since the grooved pipe connection operation is simple, it saves labor and time, so it has good economic benefits. Many articles have conducted economic analysis and believe that "although the price of a single clamp is higher, the overall benefits of the entire pipe network installation are higher than that of a flange connection". In the comparison, the articles all treated the flange connection with secondary galvanizing (which is also required according to the specifications).
6. Scope of application of grooved pipe connection
As an advanced pipe connection method, grooved pipe connection can be laid open or buried, with both rigid joints and flexible joints. Therefore, it has a wide range of applications.
(1) According to the system: it can be used for fire water systems, air conditioning hot and cold water systems, water supply systems, petrochemical pipeline systems, thermal power and pipeline systems, sewage treatment pipeline systems, etc.;
(2) According to the pipe material: it can be used to connect steel pipes, copper pipes, stainless steel pipes, plastic-lined steel pipes, ductile iron pipes, thick-walled plastic pipes, and hoses and valves with steel pipe joints and flange joints.
